The present invention relates to speech recognition for recognizing a speech uttered as one of the reference patterns registered and, in particular, to a speech recognition method and a system reducing interference caused by noise accompanying the speech uttered.
In a known speech recognition system, a speech uttered is converted into an input speech signal by an electromechanical transducer such as a microphone. The input speech signal is analyzed by a pattern analyzer and is converted into a digital input pattern signal. The input pattern signal is memorized in an input memory as a memorized pattern. The memorized pattern is compared with each of reference patterns registered in a reference memory and a dissimilarity is produced therebetween. When a particular one of the reference patterns provides the minimum dissimilarity, the speech uttered is recognized as the particular reference pattern. Alternatively, when a specific one of the reference patterns provides a specific dissimilarity smaller than a predetermined threshold value, the speech uttered is recognized as the specific reference pattern.
In actual recognition operation, the input speech signal is accompanied with noise due to the presence of background sound. The input speech signal and the noise are collectively referred to as an input sound signal. Accordingly, the input pattern signal includes a noise component. This results in a failure of the speech recognition.